[Xen-devel] [PATCH 3/4] xen/blkback: Move processing of BLKIF_OP_DISCARD from dispatch_rw_block_io

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

. and move it to its own function that will deal with the
discard operation.

Suggested-by: Jan Beulich <JBeulich@xxxxxxxxxx>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
---
 drivers/block/xen-blkback/blkback.c |   54 +++++++++++++++-------------------
 1 files changed, 24 insertions(+), 30 deletions(-)

diff --git a/drivers/block/xen-blkback/blkback.c 
b/drivers/block/xen-blkback/blkback.c
index 9d2261b..b058de7 100644
--- a/drivers/block/xen-blkback/blkback.c
+++ b/drivers/block/xen-blkback/blkback.c
@@ -416,12 +416,16 @@ static int xen_blkbk_map(struct blkif_request *req,
        return ret;
 }
 
-static void xen_blk_discard(struct xen_blkif *blkif, struct blkif_request *req)
+static int dispatch_discard_io(struct xen_blkif *blkif,
+                               struct blkif_request *req)
 {
        int err = 0;
        int status = BLKIF_RSP_OKAY;
        struct block_device *bdev = blkif->vbd.bdev;
 
+       blkif->st_ds_req++;
+
+       xen_blkif_get(blkif);
        if (blkif->blk_backend_type == BLKIF_BACKEND_PHY) {
                unsigned long secure = (blkif->vbd.discard_secure &&
                        (req->u.discard.flag & BLKIF_DISCARD_SECURE)) ?
@@ -453,6 +457,8 @@ static void xen_blk_discard(struct xen_blkif *blkif, struct 
blkif_request *req)
                status = BLKIF_RSP_ERROR;
 
        make_response(blkif, req->u.discard.id, req->operation, status);
+       xen_blkif_put(blkif);
+       return err;
 }
 
 static void xen_blk_drain_io(struct xen_blkif *blkif)
@@ -576,8 +582,11 @@ __do_block_io_op(struct xen_blkif *blkif)
 
                /* Apply all sanity checks to /private copy/ of request. */
                barrier();
-
-               if (dispatch_rw_block_io(blkif, &req, pending_req))
+               if (unlikely(req.operation == BLKIF_OP_DISCARD)) {
+                       free_req(pending_req);
+                       if (dispatch_discard_io(blkif, &req))
+                               break;
+               } else if (dispatch_rw_block_io(blkif, &req, pending_req))
                        break;
 
                /* Yield point for this unbounded loop. */
@@ -636,24 +645,16 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
                blkif->st_f_req++;
                operation = WRITE_FLUSH;
                break;
-       case BLKIF_OP_DISCARD:
-               blkif->st_ds_req++;
-               operation = REQ_DISCARD;
-               break;
        default:
                operation = 0; /* make gcc happy */
                goto fail_response;
                break;
        }
 
-       if (unlikely(operation == REQ_DISCARD))
-               nseg = 0;
-       else
-               /* Check that the number of segments is sane. */
-               nseg = req->u.rw.nr_segments;
+       /* Check that the number of segments is sane. */
+       nseg = req->u.rw.nr_segments;
 
-       if (unlikely(nseg == 0 && operation != WRITE_FLUSH &&
-                               operation != REQ_DISCARD) ||
+       if (unlikely(nseg == 0 && operation != WRITE_FLUSH) ||
            unlikely(nseg > BLKIF_MAX_SEGMENTS_PER_REQUEST)) {
                pr_debug(DRV_PFX "Bad number of segments in request (%d)\n",
                         nseg);
@@ -714,7 +715,7 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
         * the hypercall to unmap the grants - that is all done in
         * xen_blkbk_unmap.
         */
-       if (nseg && xen_blkbk_map(req, pending_req, seg))
+       if (xen_blkbk_map(req, pending_req, seg))
                goto fail_flush;
 
        /*
@@ -746,23 +747,16 @@ static int dispatch_rw_block_io(struct xen_blkif *blkif,
 
        /* This will be hit if the operation was a flush or discard. */
        if (!bio) {
-               BUG_ON(operation != WRITE_FLUSH && operation != REQ_DISCARD);
+               BUG_ON(operation != WRITE_FLUSH);
 
-               if (operation == WRITE_FLUSH) {
-                       bio = bio_alloc(GFP_KERNEL, 0);
-                       if (unlikely(bio == NULL))
-                               goto fail_put_bio;
+               bio = bio_alloc(GFP_KERNEL, 0);
+               if (unlikely(bio == NULL))
+                       goto fail_put_bio;
 
-                       biolist[nbio++] = bio;
-                       bio->bi_bdev    = preq.bdev;
-                       bio->bi_private = pending_req;
-                       bio->bi_end_io  = end_block_io_op;
-               } else if (operation == REQ_DISCARD) {
-                       xen_blk_discard(blkif, req);
-                       xen_blkif_put(blkif);
-                       free_req(pending_req);
-                       return 0;
-               }
+               biolist[nbio++] = bio;
+               bio->bi_bdev    = preq.bdev;
+               bio->bi_private = pending_req;
+               bio->bi_end_io  = end_block_io_op;
        }
 
        /*
-- 
1.7.7.3


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